[ncl-talk] Time dimension in output to NetCDF

[Dr. Muhammad Afzaal]

Thank you Dannis and Dave for your suggestion/corrections, which really
helped me understand the issue.


*Dr. MUHAMMAD AFZAAL KARORI*
Pakistan Meteorological Department
Sector H-8/2, Pitras Bukhari Road,
Islamabad - 44000
Pakistan



On Thu, Nov 30, 2017 at 5:38 PM, Dennis Shea <shea at ucar.edu> wrote:

> I don't know GrADS and how it handles 'time'
>
> ===
> My speculation is that
>       prc&time = (/ yyyymm /)
> is the source of the problem.
>  Likely, GrADS expects 'time' to have units like
> 'seconds/minutes/hours/days since ...."
>
> I would eliminate the above line .....ALso, not sure why you are
> 'promoting' the float variable to a double.
>
> GrADS questions should be sent to the GrADS support group.
> =======================
>
>   diri   = "./"
>   fili   = "precip.mon.total.v7.nc"
>   f      = addfile(diri+fili, "r")
>
>   prc    = flt2dble(f->precip(:,{12:33},{30:60}))
>   pmsg   = prc at _FillValue      ; convenience
>
> ;===============================================================
> ;write to nc file
> ;================================================================
>
>
> prc    = flt2dble(f->precip(:,{12:33},{30:60}))   ; <<< ??why are you
> promoting to double?
>
> ====
>
> Actually, the netCDF Operators could be used
>
> %> ncks --d lat,12.0,33.0 -d lon,30.0,60.0 -O precip.mon.total.v7.nc
> <http://precip.mon.total.v7.nc>prc_3mon.nc
>
> On Thu, Nov 30, 2017 at 2:17 AM, Dr. Muhammad Afzaal <
> afzaalkarori at gmail.com> wrote:
>
>> in continuation to my previous email, following is the defined variable
>> summary
>>
>> Variable: prcp
>> Type: double
>> Total Size: 27336960 bytes
>>             3417120 values
>> Number of Dimensions: 3
>> Dimensions and sizes:   [time | 1356] x [lat | 42] x [lon | 60]
>> Coordinates:
>>             time: [190101..201312]
>>             lat: [12.25..32.75]
>>             lon: [30.25..59.75]
>> Number Of Attributes: 3
>>   units :       (mm)
>>   long_name :
>>   _FillValue :  -9.969209968386869e+36
>>
>> Please read the second last line of my code as ncdf->prcp = prcp
>>
>> Thanks
>>
>> *Dr. MUHAMMAD AFZAAL KARORI*
>> Pakistan Meteorological Department
>> Sector H-8/2, Pitras Bukhari Road,
>> Islamabad - 44000
>> Pakistan
>>
>>
>>
>> On Thu, Nov 30, 2017 at 12:06 PM, Dr. Muhammad Afzaal <
>> afzaalkarori at gmail.com> wrote:
>>
>>> Dear NCL users
>>>
>>> I am using NCL 6.4.0 on ubuntu. I need to write a variable to netcdf
>>> file. I did it successfully using Method 1 given on ncl homepage. I have
>>> little problem that when I open nc file in grads, the time is not
>>> realistic. I mean its like;
>>>
>>> Time values set: 2320:6:25:0 2320:6:25:0
>>>
>>> while the variable has the time from 190101 to 201312
>>>
>>> Can someone please help me how can add time dim as that attached with
>>> the define variable? My code is given below
>>>
>>> ;====================================================
>>> begin
>>>
>>>   diri   = "./"
>>>   fili   = "precip.mon.total.v7.nc"
>>>   f      = addfile(diri+fili, "r")
>>>
>>>   prc    = flt2dble(f->precip(:,{12:33},{30:60}))
>>>   pmsg   = prc at _FillValue      ; convenience
>>>
>>> ;*********************************
>>> ; plot parameters
>>> ;*********************************
>>>   dimprc = dimsizes(prc)
>>>   ntim   = dimprc(0)
>>>   nlat   = dimprc(1)
>>>   mlon   = dimprc(2)
>>>
>>>   tim  = f->time
>>>   utc_date = cd_calendar(tim, 0)
>>>   year    = tointeger(utc_date(:,0))
>>>   yrStrt  = year(0)
>>>   yrLast  = year(ntim-1)
>>>   nyear   = yrLast-yrStrt+1
>>> ;print(year + " " + yrStrt + " "+ yrLast +" "+ nyear)
>>>   yyyymm  = yyyymm_time(yrStrt, yrLast, "integer")
>>>
>>>   yrfrac  = (/ yyyymm_to_yyyyfrac(yyyymm, 0.0) /)
>>>   prc&time = (/ yyyymm /)
>>>
>>> ;===============================================================
>>> ;write to nc file
>>> ;================================================================
>>>
>>>     system("/bin/rm -f prc_3mon.nc") ;remove any pre-existing file
>>>     ncdf = addfile("prc_3mon.nc" ,"c") ; open output netCDF file
>>>
>>> ;===============================================================
>>> ; create global attributes of the file (optional)
>>> ;================================================================
>>>        fAtt               = True        ; assign file attributes
>>>        fAtt at title         = "GPCC Rainfall"
>>>        fAtt at source_file   = "precip.mon.total.v7.nc"
>>>        fAtt at Conventions   = "None"
>>>        fAtt at creation_date = systemfunc ("date")
>>>        fileattdef( ncdf, fAtt )           ; copy file attributes
>>>
>>> ;===============================================================
>>> ; make time an UNLIMITED dimension;recommended for most applications
>>> ;===============================================================
>>>
>>>        filedimdef(ncdf,"time",-1,True)
>>>
>>> ;===============================================================
>>> ; output variables directly; NCL will call appropriate functions
>>> ; to write the meta data associated with each variable
>>> ;===============================================================
>>>        ncdf->spi  = spi                          ; 3D
>>> end
>>>
>>>
>>> Regards
>>> *Dr. MUHAMMAD AFZAAL KARORI*
>>> Pakistan Meteorological Department
>>> Sector H-8/2, Pitras Bukhari Road,
>>> Islamabad - 44000
>>> Pakistan
>>>
>>>
>>>
>>
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>
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